DNA pattern of human pituitary tumors

Pathogenesis, clinical features, and treatment of plurihormonal pituitary adenoma

Plurihormonal pituitary adenoma (PPA) is a type of pituitary tumor capable of producing two or more hormones and usually presents as an aggressive, large adenoma. As yet, its pathogenesis remains unclear. This is the first study to systematically summarize the underlying pathogenesis of PPA. The pathogenesis is related to plurihormonal primordial stem cells, co-transcription factors, hormone co-expression, differential gene expression, and cell transdifferentiation. We conducted a literature review of PPA and analyzed its clinical characteristics. We found that the average age of patients with PPA was approximately 40 years, and most showed only one clinical symptom. The most common manifestation was acromegaly. Currently, PPA is treated with surgical resection. However, recent studies suggest that immunotherapy may be a potentially effective treatment.

Molecular defects in the pathogenesis of pituitary tumours

The majority of pituitary adenomas are trophically stable and change relatively little in size over many years. A comparatively small proportion behave more aggressively and come to clinical attention through inappropriate hormone secretion or adverse effects on surrounding structures. True malignant behaviour with metastatic spread is very atypical. Pituitary adenomas that come to surgery are predominantly monoclonal in origin and roughly half are aneuploid, indicating either ongoing genetic instability or transition through a period of genetic instability at some time during their development. Few are associated with the classical mechanisms of tumour formation but it is generally believed that the majority harbour quantitative if not qualitative differences in molecular composition compared to the normal pituitary. Despite their prevalence and the ready availability of biopsy material, at the present time, the precise molecular pathogenesis of the majority of pituitary adenomas remains unclear. This review summarizes current thinking.

The study of endocrine tumors by flow and image cytometry

Both DNA flow and image cytometry are methods that can be used for the quantitative determination of cellular DNA content. Objective, quantitative analysis of cellular morphology can also be obtained using image cytometry. Data thus generated have been shown to be of diagnostic and prognostic use in the study of many solid tumors and would be of particular value in the evaluation of endocrine tumors that show a poor correlation between their histology and biological behavior. The main application of these techniques to endocrine tumors has been in the analysis of thyroid nodules, although a limited number of studies of parathyroid, pituitary, adrenal, and pancreatic neuroendocrine tumors and tumors of the dispersed neuroendocrine system have been reported. Review of these studies shows that in the endocrine organs DNA and morphometric measurements have a very limited role in the diagnosis of individual cases, but are important as prognostic variables. The high incidence of abnormal DNA content in histologically benign lesions of the endocrine glands has important biological implications. Further investigation of this phenomenon may help to elucidate the process of endocrine tumorigenesis.

Glucocorticoid incubation of human ACTH-producing pituitary tumours in vitro. A study on ACTH secretion and cell morphology

ACTH-producing pituitary adenomas obtained from two patients with Cushing's disease were maintained in organ culture for 2 weeks. After 4-6 days of incubation, hydrocortisone (0.1, 1, and 5 mg/ml) was added to the culture medium. Addition of cortisol to the media in concentrations which generally inhibit the ACTH secretion in vivo in patients with Cushing's disease (1 mg/ml) failed to affect the ACTH secretion in vitro. A decrease of ACTH secretion occurred only with 5 mg/ml after 5 days of incubation. A similar effect on growth hormone (GH) release was seen when cortisol (10 mg/ml) was added to cultures from GH-producing pituitary adenoma. No ultrastructural changes were found in cultured cells that could be attributed to the addition of 0.1 mg/ml cortisol in the culture medium. With higher concentrations, (1 mg/ml and 5 mg/ml) minor ultrastructural changes were suspected. Our present findings implicate the hypothalamus as the target area for the feedback control of ACTH in Cushing's disease but could not reveal whether or not the primary lesion (i.e. the tumor) was of pituitary or hypothalamic origin. Our organ culture system appears to be a suitable model for investigating possible ACTH-regulating factors.